In addition to an antenna for transmitting or receiving radar or microwaves, known filling level measuring instruments have a frequency converter, which transforms an electromagnetic signal, which was generated by a transmit pulse oscillator, into high frequencies.
The document DE 43 31 353 relates to a radar distance measuring instrument with a frequency conversion circuit having a local oscillator, a mixer and an antenna port. The frequency conversion circuit converts a frequency of the signals received by a radar module by mixing with another frequency of the local oscillator into a higher frequency, with which the transmit signals are delivered to an antenna port.
Herein, the transmitting power depends on the power of the mixer. After leaving the mixer, there is no way to amplify the transmit signal again.